Search PubMed⌕ Search

Biomedical subjects

P Rioux

Publications and source records attributed to P Rioux.

7 recordsLinked to original sources
PubMed1992

Central benzodiazepine receptors in human brain: estimation of regional Bmax and KD values with positron emission tomography.

Studies of central benzodiazepine receptors in the human brain in vivo are now possible using positron emission tomography (PET) and [11C]flumazenil. With the aim of measuring Bmax and Kd in brain regions, we used a two-injection [11C]flumazenil (at high and low specific radioactivity, respectively) pseudo-equilibrium paradigm to evaluate, in seven unmedicated healthy volunteers, the relative merits of three 'reference' structures (pons, hemispheric white matter and corpus callosum) in which the free radioligand concentration in brain tissue was estimated 15-40 min after i.v. injection of the radioligand. By means of high-resolution PET, the Bmax and Kd were calculated for each subject in 18 gray matter structures, based on a two-point Scatchard plot. We found that the use of the corpus callosum as reference often resulted in spurious Bmax and Kd values. The pons was the best reference structure because it provided satisfactory Bmax values (closest to in vitro data) and most consistent Kd values, and was the region easiest to sample on PET images. The pattern of regional Bmax was consistent with that expected from in vitro studies, with values highest in the cerebral cortex, intermediate in the cerebellum, and lowest in the striatum and the thalamus. The Kd values were uniform among regions and were consistent with earlier in vitro and in vivo data. This work documents the feasibility of estimating Bmax and Kd of central benzodiazepine receptors in multiple brain regions for clinical research.

Adult↗
PubMed1992

Regional cerebral oxygen consumption, blood flow, and blood volume in healthy human aging.

Using high-resolution positron emission tomography and the oxygen 15 continuous inhalation method, we examined the changes in cerebral metabolic rate of oxygen, blood flow, blood volume, and oxygen extraction fraction as a function of age in 25 optimally healthy, unmedicated volunteers who ranged in age from 20 to 68 years. Subjects were strictly selected for absence of cerebrovascular risk factors, dementia, or mental disorders; they had neither biological nor clinical abnormalities, and no focal anomaly on computed tomographic scan. Regions of interest were determined according to the anatomical structures defined on corresponding computed tomographic scan cuts obtained using a stereotaxic head-positioning method. This same method was also used for positron emission tomographic imaging. There was no significant effect of aging on PaCO2 values, hematocrit, arterial blood pressure, cholesterol and triglyceride levels, and blood glucose levels. In most cerebral cortex gyri, the cerebral metabolic rate of oxygen significantly decreased with age according to a linear pattern, with the same magnitude (about -6% per decade) in all four lobes and on both sides. This effect of age on cortical cerebral metabolic rate of oxygen persisted when the possible influence of cortical atrophy, gender, and head size were partialled out. In contrast, the white matter, deep gray nuclei, thalamus, and cerebellum were not significantly affected. The cerebral blood volume declined with a similar pattern to cerebral metabolic rate of oxygen, while changes in cerebral blood flow were less significant, presumably because of larger variance of data across subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Thrombi of the right heart. Value of thrombolytic therapy in mobile thrombi].

Seven patients with mobile right heart thrombi, 4 floating and 3 pediculated, were recensed between 1985 and 1990. Two patients were admitted for congestive cardiac failure (Group I) and 5 patients for pulmonary embolism (Group II). Both patients in Group I were treated with heparin without complications. In one case, the size of the thrombus decreased in 10 days whereas, in the second case, it disappeared within 8 days. In Group II, the first patient underwent successful thrombectomy. The other four patients were given thrombolytic therapy (UK = 2, rt-PA = 2) associated with appropriate doses of heparin. In the two patients given UK (3M units the first day followed by 1.2 M units per day for 4 days) the thrombus disappeared in the first 48 hours of treatment. One patient had a recurrent pulmonary embolism after 2 hours' treatment; both patients had a fall in haemoglobin of 3 cg/ml at the second day. The second patient died at the 5th day. In the two patients treated by rt-PA (100 mg/7 hours) the thrombus disappeared within 4 hours of starting therapy. One patient had a probable recurrent pulmonary embolism. Both patients had a fall in haemoglobin of 3 cg/ml at the 2nd day of treatment. Right heart thrombi are rare (168 cases in the literature of which 111 were mobile). The prognosis seems to be related to echocardiographic appearances: mortality of mural thrombi is about 4% compared with 50% in mobile thrombi. Very mobile "worm-like" masses are therapeutic emergencies because of the risk of embolism (about 68%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Angioplasty after failure of thrombolysis in myocardial infarction. Hospital results apropos of 40 consecutive patients].

Intravenous thrombolysis during the acute phase of myocardial infarction is successful in restoring perfusion in 60 to 80% of cases. When it is unsuccessful, there is disagreement about the best approach to adopt. The article reports the results obtained in 40 consecutive patients treated by angioplasty after thrombolysis had been unsuccessful. Reperfusion was achieved in 92.5% of cases, with a hospital mortality rate of 7.5% (2.5% if patients admitted in a stage of cardiogenic shock are excluded). There was no mortality related to the procedure itself and an emergency aorto-coronary by-pass was not required in any case. Since it is accepted that the subsequent prognosis depends on coronary patency, coronary artery assessment after thrombolysis, followed by angioplasty if the occlusion persists seems to be a logical strategy if the myocardial territory is compromised.

Adult↗
PubMed1979

Discriminant analysis: methods and program.

Because of the disparity in the results obtained using different methods of discriminant analysis, we have written and used a unique program to test them. These methods can be divided into two groups corresponding to a classical probabilistic approach (i.e., Bayesian methods) or a topological approach (i.e., Sebestyen method).

Bayes Theorem↗
PubMed1979

Intra- and interhemispheric EEG differences quantified by spectral analysis. Comparative study of two groups of schizophrenics and a control group.

In this work we have studied comparatively the relationships between alpha intensity, alpha frequency, root-mean-square amplitude and their standard deviations, versus the location of the four recorded EEG channels: left and right rolando-parietal, left and right parieto-occipital. Twenty-four spectral parameters were computed for each 5-min EEG recording, in the eyes closed situation. The hebephrenic group (36 EEGs from six patients) presented higher values of alpha intensity and RMS amplitudes with low coefficient of variation when compared with the other groups. The left/right rolando-parietal amplitude ratio was 0.73 versus 1.52 for the parieto-occipital ratio. An amplitude hypovariability in the central regions, probably associated with hyperarousal, especially in the left hemisphere, can then be observed in hebephrenics, together with high alpha intensity on the left parieto-occipital area. The two groups of schizophrenics differ from the control group (27 EEGs from 12 subjects) in terms of spectral parameters, the hebephrenic group presenting a possible interhemispheric dysfunction.

Adult↗